Three dialysis providers have received subpoenas about their dealings with a premium assistance program that's been under increasing scrutiny from both private and public payers.

In Fresenius Medical Care Holdings' announcement and DaVita’s announcement, they reveal that they’ve been subpoenaed by the U.S. Attorney for the District of Massachusetts, which has asked for information about their involvement with the premium assistance program operated by the American Kidney Fund. Both indicated they are cooperating with the investigation.

The companies also announced that they’ve joined in a lawsuit representing dialysis patients and providers against a recently released interim final rule that aims to stop dialysis providers from steering patients to higher-reimbursement Affordable Care Act plans.

In that rule, the Centers for Medicare & Medicaid Services says it learned that it is common for dialysis facilities to involve themselves in end-stage renal disease patients’ coverage decisions, which can drive up costs for patients and jeopardize their health.

"We felt we had no choice but to challenge this hastily implemented rule to protect the interests of our patients and those of the greater kidney care community," said Philipp Stephanus, senior vice president in charge of patient support functions at DaVita.

American Renal Associates Holdings, meanwhile, received its own subpoena from the Justice Department, it revealed in a Securities and Exchange Commission filing. The company says the DOJ wants information about its interaction with the American Kidney Fund and “certain topics related to applicable healthcare laws” from as far back as 2013, adding that it will cooperate with federal authorities.

UnitedHealth sued American Renal Associates this past summer, accusing it of convincing Medicare- and Medicaid-eligible patients with kidney failure to obtain coverage with the insurer in order to obtain higher reimbursement.